Recycle process for a metal bearing sludge concentrate

ABSTRACT

A recycling treatment of heavy metal sludge uses a cracking process which releases macromolecular agglutinant and a metal hydrate mixture. Next the mixture is acidified in a primary homogenization process and then a primary separation process separates the macromolecular agglutinant and acid solution with metal ions. A second homogenization process adjusts the pH value of the acid solution with metal ions to be alkaline and then a second separation process separates copper oxide and the remaining salt solution with oxidant. Lastly, salt compounds and oxidant solution is separated through the use of a crystal separation process.

[0001] The recycling treatment of heavy metal sludge includes: thecracking process, the primary homogenization process, the primaryseparation process, the secondary homogenization process, the secondaryseparation process and the crystal separation process. The crackingprocess is used to mix the sludge with acid solution and peroxideproportional to the sludge in weight. The mixture is then treated underhigh temperature and normal pressure. Macromolecular agglutinant andmetal ion mixture will be released after a certain period of reaction.Next, the resulting mixtures go through the processes of primaryhomogenization and primary separation to separate macromolecularagglutinant which can then be used in sewage treatment system. Further,the secondary homogenization process and the secondary separationprocess will separate metal oxide while the process of crystalseparation will filter out neutralization material that can be appliedin soil or other exhausted liquid along with an oxidant that can be usedfor water treatment. The metal oxides and macromolecular agglutinant arethus recycled and reused while other end products are used in thistreatment system or the sewage treatment system to avoid causing furtherenvironmental pollution. Also, production cost is lowered and resourcesare recycled.

FIELD OF INVENTION

[0002] The invention involves the recycling treatment of sludgecontaining heavy metal, in particular a treatment that can recycle andreuse the heavy metal sludge and the exhausted liquid of etchingsolution generated in the process of producing printed circuit boards.The solid metal oxide, liquid treating compound and agglutinant producedin the treatment can be recycled and used in the process, the sewagetreatment system or other uses. This treatment is a method that treatsand recycles heavy metal sludge without causing further pollution.

BACKGROUND

[0003] Circuit board manufacturing has played an important role in thestrategic industry in Taiwan. It is considered an essential industrythat will allow Taiwan to become an island of technology. However, thesludge and the etching solution of different concentrations generated inthe process are classified as hazardous waste. Hence, despite the highgrowth and high profitability, the industry has long been troubled withthe problem of causing environmental pollution. According to domesticstatistics, the circuit board manufacturing industry produces more than200,000 tons of hazardous sludge every year. This number increases 20%every year. What is more, the organic or inorganic chemicals used byvarious production units in the printed circuit board manufacturingprocess also generate exhausted liquid of high concentration, includingthe exhausted liquid of developer, the exhausted liquid of stripping,the exhausted liquid of etching solution and the exhausted liquid ofstannum and lead stripping. Thus, the industry has long tried toeffectively resolve the problems of heavy metal sludge and exhaust gas.

[0004] In Taiwan and in other countries, many methods have beendeveloped to handle heavy metal sludge, which includes burial,calcinations, solidification, fusion, acid maceration and ammonia leach.For all relevant technology, please refer to Patent No. GE844722 of UK,Patent Nos. 3,300,299, 4,428,773, 4,242,127, 4,162,294, 5,599,458,5,807,478 and 5,234,669 of USA as well as U.S. Pat. Nos. 81,106,585,82,103,460, 89,123,260, 89,112,071, 89,116,503 of the Republic of China.Nevertheless, none of these methods can avoid the problem of causingfurther environmental pollution, i.e. none of these methods cancompletely eliminate hazardous exhaust gases, wastewater and wastecreated during or after the treatment. Instead, these treatments cansimply reduce the amount of hazardous materials to an acceptable degree.The hazardous materials are then disposed of by a professional cleaninginstitution according to relevant laws and regulations. Possible risksof such treatments include water or land pollution when hazardousmaterials are disposed or buried at discretion or were not transportedto the designated disposal area. Besides, such methods also waste a lotof resources. So far, current heavy metal sludge treatments cannot solvesuch problems.

[0005] In addition to the problem of environmental pollution, the highcost of treatment is also a heavy burden to the industry. At present,the only method recognized by the government is solidification whosetreatment cost reaches 10-12 NT$/kg (excluding the cost of cleaning andburial). For a company that might have to dispose of several tones ofsludge every day, the cost of treatment is nearly unbearable. Thus, suchmethod of treatment is not cost efficient, nor does it fit in the goalof enterprises to reuse resources for sustainable development.

[0006] [Goal]

[0007] The goal of this invention is to provide a method to treat and torecycle heavy metal sludge. The process of such treatment can establisha complete lifespan cycle of waste to recycle and reuse treatmentproducts in different units or to use them in sewage treatment systemsor recycle system so as to avoid causing further environmentalpollution.

[0008] Another objective of this invention is to lower the productioncost, to increase the production efficiency and to reduce the amount ofwaste for enterprises' goal of sustainable development.

[0009] [Description]

[0010] The major feature of this heavy metal sludge treatment is theinclusion of the cracking process, in which sludge is mixed with acidsolutions such as sulphuric acid, nitric acid and hydrochloric acid aswell as peroxides such as hydrogen peroxide, dibutyl peroxide, bicumylperoxide, (tertbutyl peroxide) hexene and (tertbutyl peroxide) hexane inan amount proportional to the amount of sludge. The mixture is stirredand treated under high temperature and normal pressure. After four hoursof reaction, the heavy metal in the mixture is released whilemacromolecular agglutinant in the sludge mixture is broken by peroxideand release heavy metal hydrate, which then reacts with acid solution torelease metal ions.

[0011] Based on the above-mentioned feature, the weight ratio ofperoxide to sludge is 0.5-2 to 40-50.

[0012] Another feature of this invention is the inclusion of the primaryhomogenization process and the primary separation process which can usean acid solution to treat the mixture after the cracking process tochange the pH value of the mixture to be between 2 and 7 and separatemacromolecular agglutinant that contains 70% water as well as an acidsolution with heavy metal ions. The macromolecular agglutinant can thenbe recycled and used in a sewage treatment system.

[0013] The next feature of the invention is to further include theprocesses of secondary homogenization and secondary separation, whichadd ammonia, and Alkaline Earth Metal into the acid solution with heavymetal ions generated in the primary separation process so as to changethe pH value of the solution to be between 7 and 11. The crystallinedeposit process then separates metal oxides and salt solutionscontaining oxidant. Metal oxides can be used as the raw material forchemical processing or otherwise recycled.

[0014] The invention further includes the process of crystal separationto freeze and crystallize the salt solution that contains oxidant afterthe secondary separation process and to separate salt compounds. Thesalt compounds can be recycled and reused in soil treatment or otherindustries while the remaining oxidant solution can be used directly inthe cracking process or used as an oxidant in water treatment after thesolution reaches a certain concentration.

[0015] The last feature of this invention is to include the digestingprocess to direct the exhausted liquid into the cracking process or touse normal acid to mix with the mixture of sludge.

[0016] The digesting process can further mix the hydrate treated in theprimary separation process with the sludge mixture in the primaryhomogenization process and/or the secondary homogenization process.

DESCRIPTION OF FIGURES

[0017]FIG. 1 is the flowchart of the first example of the heavy metalsludge recycling treatment.

[0018]FIG. 2 is the flowchart of the second example of the heavy metalsludge recycling treatment.

[0019]FIG. 3 is the flowchart of the third example of the heavy metalsludge recycling treatment.

DESCRIPTION OF EXAMPLES

[0020] Please refer to FIG. 1 for the heavy metal sludge recyclingtreatment which includes the cracking process (2), the primaryhomogenization process (3), the primary separation process (4), thsecondary homogenization process (5), the secondary separation process(6), the crystal separation process (7) and the digesting process (8).The flow diagram is illustrated below:

[0021] In the cracking process (2), the tank containing the treatingcompound (20) is used to store peroxide. In this example, dibutylperoxide (or any peroxide sold in the market such as hydrogen peroxide,bicumyl peroxide, (tertbutyl peroxide) hexane, or (tertbutyl peroxide)hexane are used. The sulphuric acid solution tank (21) is used to storesulphuric acid solution while the reaction tank (22) has a beater to mixthe sludge and the above-mentioned solution. In this process, 40 kg ofdibutyl peroxide (or any other peroxide) and 200 kg of sulphuric acidsolution are put in the reaction tank (22), then 1000 kg of sludge with10% of copper (9) is put into the reaction tank (22). The mixture of1240 kg is then stirred while the temperature is increased to 220° C.After four hours of reaction under normal pressure, the metal in thesludge that can't be solved by the sulphuric acid solution is thenreleased and the macromolecular agglutinant in the sludge mixture isdestroyed by organic peroxide to release m tal hydrate in the sludge.The weight ratio of peroxide and sludge is 0.5-2 to 40-50. Aftertreatment, the mixture goes through the primary homogenization process(3).

[0022] In the process of primary homogenization (3), a digestion tank(30) is used to store an acid solution, such as sulphuric acid. It isnoteworthy that the digesting process (8) of this invention uses adigesting liquid tank (80) to store the exhausted liquid of microetching for recycling. The tank also stores the acid solution (orhydrate) containing copper ions after the primary separation process (4)to be described later so as to be directly used in the digestion tank(30) or to be stored in the sulphuric acid solution tank (21). To betterenhance the treatment of filter press in the primary separation process(4), the pH value of the 1240 kg of sludge mixture treated in thecracking process (2) is adjusted to be between 2 and 7. In this example,600 kg of acid solution is used to mix with the sludge mixture and thepH value is adjusted to 5. 950 kg of macromolecular agglutinantcontaining 70% water and 600 kg of acid solution with copper ions arefiltered out. Among which, the macromolecular agglutinant can berecycled and used in sewage treatment systems.

[0023] In the secondary homogenization process (5), a precipitator tank(50) and a precipitation tank (51) are used. The precipitator tank (50)can store alkaline solution such as lime, sodium hydroxide, ammonia foruse in the precipitation tank (51). In this example, 50 kg of lime isadded in the 600 kg of acid solution with copper ions filtered duringthe primary separation process (4) to create a 650 kg of mixture. The pHvalue of the mixture is adjusted to be between 7 and 9 after the filterpress treatment in the secondary separation process (6) to precipitate250 kg of 50% copper oxide and 400 kg of remaining alkaline solution.Copper oxide can then be used as raw material in the chemical industryor copper industry.

[0024] Finally, after the crystal separation process (7), the tank thatstores alkaline solution with a sulfate radical (70), the crystallizertank (71) and centrifugal filter (72) filter out sulphate and peroxidesolution from the remaining digesting liquid after the secondaryseparation treatment. Filtered sulphate can be recycled and used as rawmaterial for industrial usage or civil usage while the remainingperoxide solution can be led into the treating compound tank (20) forthe cracking process (2) after the pH value is adjusted to be neutral.It can also be used as an oxidant for water treatment.

[0025] From the flowchart, we can see that during each part of thetreatment process of the sludge with copper, all products were eitherreused in the process or led into a sewage treatment system or recycledback into the system for further use. Hence, the problem of causingfurther pollution is resolved.

[0026]FIGS. 2 and 3 are the second and third example of this invention.The second example includes the cracking process (2′), the primaryhomogenization process (3′), the primary separation process (4′), thesecondary homogenization process (5′), the secondary separation process(6′) and the crystal separation process (7′) as well as the digestingprocess. However, the digesting process (8′) is different from exampleone while the other processes are exactly the same. In example two, thedigesting process is divid d into two. One tank of micro etchingexhausted liquid (81′) is used to store micro etching exhausted liquidwith copper (hereinafter as micro etching bath) from a factory ofprinted circuit board and a tank of digesting liquid (82′) for the acidsolution with copper ions after the treatment of primary separation(4′). Example three also includes the cracking process (2″), the primaryhomogenization process (3″), the primary separation process (4″), thesecondary homogenization process (5″), the secondary separation process(6″), the crystal separation process (7″) and the digesting process. Theonly difference is that the digesting process is divided into threeparts with th micro etching exhausted liquid tank (81″) and th digestingliquid tank (82″) in example two and a tank containing etching exhaustedliquid (83″). All the other processes are exactly the same as exampleone.

[0027] In addition, example four used hydrogen peroxide as the peroxidewhile the other processes are the same as examples one, two, and three.Example five used hydrochloric acid for the acid solution and examplesix used limes as the precipitator, all the other processes are thesame.

[0028] For example seven, eight and nine, all the processes are the sameexcept that example seven used a dibutyl peroxide with the ratio of 1-5to 5-1, example eight used tertbutyl peroxide ethene for its peroxide,and example nine used nitric acid as the acid digesting liquid andammonia as the precipitator.

[0029] As for the products of all the examples, the analysis of copperoxide is shown in Table 1 and the results of function testing ofmacromolecular agglutinant and oxidant are shown in Table 2. TABLE 1Example Cu (%) Fe (ppm) Sn (ppm) Ni (ppm) Zn (ppm) Pb (ppm) Salt 1 36.73903.15 2837.6 683.4 481.2 103.4 sodium sulphate 2 37.24 914.22 2854.2672.6 489.5 107.2 sodium sulphate 3 28.01 898.63 2812.9 693.5 498.3115.8 ammiaonia sulfate 4 42.33 951.78 2962.1 722.2 535.6 137.2 calciumchloride 5 43.57 966.69 2945.8 737.8 547.2 142.6 calcium chloridecalcium sulphate 6 43.46 942.59 2973.9 713.9 551.5 132.6 ammoniumchloride 7 41.39 875.34 2621.7 654.3 461.7 87.7 ammonium nitrate 8 40.99879.12 2654.8 662.4 453.4 91.4 ammonium nitrate ammiaonia sulfate 941.83 869.37 2663.2 649.1 442.2 80.6 ammonium nitrate

[0030] TABLE 2 Macromolecular Example agglutinant (Note 1) % Oxidant(Note 3) % 1 4.7 (25) (Note 2) 6.7 2 4.2 (27) 7.0 3 5.0 (22) 6.9 4 — 4.25 — 4.6 6 — 4.5 7 3.2 (31) 5.3 8 3.5 (33) 5.9 9 3.1 (30) 6.4

[0031] In sum, this invention of heavy metal sludge recycling treatmentis not only creative and innovative, but also fits the need of theindustry. Please note the above-mentioned examples are just some of thebest examples and the scope of patent of this invention should not belimited to these examples. Any change or modification made based on thisinvention should be within the scope of patent of this invention.[Reference list of component symbols] the cracking process 2, 2′, 2″ theprimary 3, 3′, homogenization process 3″ the primary separation 4, 4′,process 4″ the secondary 5, 5′, homogenization process 5″ the secondaryseparation 6, 6′, process 6″ the crystal separation 7, 7′, process 7″the digesting process 8 the tank of treating 20 the tank of 21 compoundsulphuric acid solution the reaction tank 22 the digestion 30 tank theprecipitator tank 50 the precipitation 51 tank the liquid tank 70 thecrystallizer 71 tank the centrifugal filter 72 the tank of micro 81′,etching exhausted 81″ liquid the tank of digesting 82′, liquid 82″ tankof etching 83′, exhausted liquid 83″

1. A recycling treatment of heavy metal sludge which includes: Thecracking process, in which the sludge is mixed with a sulphuric acidsolution and peroxide proportional to the sludge in weight and treatedunder high temperature and normal pressure, After a certain period ofreaction, macromolecular agglutinant and a metal hydrate mixture arereleased; The primary homogenization process, which adjusts the pH valueof the mixture after the cracking process to be acidic; The primaryseparation process, which mixes the acid mixture from the primaryhomogenization process to separate macromolecular agglutinant and acidsolution with metal ions; The second homogenization process, whichadjusts the pH value of the acid solution with metal ions to bealkaline; The second separation process, which separates copper oxideand the remaining salt solution with oxidant after secondhomogenization; and The crystal separation process, which treats theremaining acid exhausted liquid after second separation to filter outsalt compounds and oxidant solution.
 2. For the cracking processmentioned in claim 1 of the heavy metal sludge recycling treatment, theweight ratio of peroxide and sludge is 0.5-2 to 40-50.
 3. The peroxideused in the cracking process mentioned in claim 1 of the heavy metalsludge recycling treatment can be hydrogen peroxide, dibutyl peroxide,dicumyl peroxide, (tertbutyl peroxide) hexene, (tertbutyl peroxide)hexane.
 4. The primary homogenization process mentioned in claim 1 usesone or more acid solution including sulphuric acid, hydrochloric acid,nitric acid and micro etching exhausted liquid to change the pH value.5. The secondary homogenization process mentioned in claim 1 uses one ormore alkaline solution including sodium hydroxide, lime, ammonia andetching exhausted liquid to change the pH value.
 6. The temperature usedin the cracking process mentioned in claim 1 is between 200° C. and 250°C.
 7. The time needed for the process of cracking mentioned in claim 1is three to six hours.
 8. The best pH value for primary homogenizationprocess mentioned in claim 1 should be 2 to
 7. 9. The best pH value forsecondary homogenization process mentioned in claim 1 should be 7 to 10.10. The products of the crystal separation process mentioned in claim 1include: sodium sulphate, ammiaonia sulfate, sodium chloride, sodiumchloride, sodium nitrate, ammonium nitrate, calcium sulphate and calciumchloride.
 11. The digesting process mentioned in claim 1 is used to mixeither the existing micro etching exhausted liquid from a printedcircuit board factory or any normal acid with the sludge mixture in theprocess of cracking.
 12. The digesting process mentioned in claim 1 canfurther use the hydrate treated in primary separation or the hydrate canbe used in the primary homogenization and/or secondary homogenization tobe mixed with the sludge mixture.
 13. The copper oxide produced in theprocess as described in claim 1 contains a copper content of 30-50% ofits weight.
 14. For the macromolecular agglutinant mentioned in claim 1in the patent application, the content of macromolecule is 20-40% inweight.
 15. For the oxidant solution mentioned in claim 1 in the patentapplication, the oxidizing ability can reach the standard of sewagedischarge of COD 200 to 500 ppm after adding 3.0-9.0 permillage inweight.